iSCSI vs. Fibre Channel

We’ve had several posts here about storage virtualization (a.k.a. SANs) and the role that storage virtualization plays in both server and desktop virtualization. We made the decision some time ago to promote iSCSI SAN products rather than fibre channel, primarily because iSCSI uses technologies that most IT professionals are already familiar with – namely Gigabit Ethernet and TCP/IP – whereas fibre channel introduces a whole new fiber optic switching infrastructure into your computing environment, together with the new skills required to manage it.

But there are many who maintain that, although a fibre channel SAN infrastructure may be more expensive, and may require a different set of skills to manage, it offers superior performance.

So I was particularly interested to run across an article by Greg Shields on entitled “Fibre Channel vs. iSCSI SANs: Who Cares?” I would encourage you to click through and read this article in its entirety, although you may have to register and give up your email address to do so. But here are a couple of tidbits from the article to whet your appetite:

iSCSI vs. Fibre Channel: Who cares?
The answer: Statistics suggest that it doesn’t really matter…In most real-world scenarios, the performance difference between Fibre Channel and iSCSI SANs is negligible. Partisans will extol the raw performance statistics of their favorite SAN type, but it’s fantastically difficult to translate raw performance specifications into real-world user experience…

Performance alone may not be a decisive factor, but a SAN’s ease of administration can be. The management tools and techniques for Fibre Channel and iSCSI storage infrastructures are substantially different…the skills and experience required to run a Fibre Channel storage infrastructure are difficult to come by – often requiring additional consulting support for most implementations to start correctly. On the other hand, iSCSI SANs lean heavily on the existing TCP/IP protocol. If you have network engineers in your environment, they probably possess most of the necessary skills to successfully manage an iSCSI storage infrastructure.

So, while I would once again encourage you to read Greg’s post in its entirety (so you can assure yourself that I’m not quoting him out of context), I must say that I find his comments gratifying, because they tend to reinforce our own conclusions: unless you already have a fibre channel SAN infrastructure, there’s no compelling reason not to go with an iSCSI solution, and several reasons in favor of doing so, including cost and simplicity of management.

Anybody out there disagree? And, if so, can you tell me why, exactly, you feel that fibre channel is superior?

4 replies
  1. ockveoo2
    ockveoo2 says:

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  2. John Harris
    John Harris says:

    There are a few key advantages that come to mind with VMWare ESX. Because it’s able to aggressively allocate hardware resources (CPU, RAM, disk, network), ESX can take advantage of additional bandwidth in three key areas:

    1. Increase VM Guest network traffic capacity while consolidating cabling for VM-dedicated NIC’s. In my previous environment, we were using 4 to 6 GigE interfaces for VM Guest traffic, which

    2. In a multi-VM host environment, 10GigE will increase throughput for VMotion server-to-server VM migration (in which VMWare copies the active RAM to a file on a second server), which will allow faster re-allocation of resources. This will improve VM host uptime, since VMmotion guest migration is gated on this memory-state data transfer over the network.

    3. iSCSI storage, with 10GigE interfaces, will be a powerful, flexible alternative to Fibre Channel storage.

    We have a great blog on this -please see link:

  3. Sid Herron
    Sid Herron says:

    @glihtco – the real question is whether the difference is perceivable in the real world. As Greg Shields says in the quote above, “…it’s fantastically difficult to translate raw performance specifications into real-world user experience…”

  4. glihtko
    glihtko says:

    Isn’t it so that 1G ethernet with iSCSI, with overhead of SCSI in TCP is slower that 1Gb FC ? Compared to 2Gb? 4Gb? – and price of 10Gb Eth vs 8Gb FC (Switches & HBA/NIC ) is now in favour of FC? iSCSI HW initiator 10Gb NIC is quite expensive…..

    Or not?


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